全文获取类型
收费全文 | 6268篇 |
免费 | 188篇 |
国内免费 | 29篇 |
专业分类
电工技术 | 86篇 |
综合类 | 24篇 |
化学工业 | 1681篇 |
金属工艺 | 125篇 |
机械仪表 | 228篇 |
建筑科学 | 167篇 |
矿业工程 | 4篇 |
能源动力 | 387篇 |
轻工业 | 659篇 |
水利工程 | 89篇 |
石油天然气 | 36篇 |
无线电 | 594篇 |
一般工业技术 | 1100篇 |
冶金工业 | 277篇 |
原子能技术 | 84篇 |
自动化技术 | 944篇 |
出版年
2024年 | 138篇 |
2023年 | 145篇 |
2022年 | 335篇 |
2021年 | 433篇 |
2020年 | 349篇 |
2019年 | 374篇 |
2018年 | 361篇 |
2017年 | 297篇 |
2016年 | 330篇 |
2015年 | 196篇 |
2014年 | 325篇 |
2013年 | 532篇 |
2012年 | 306篇 |
2011年 | 314篇 |
2010年 | 278篇 |
2009年 | 244篇 |
2008年 | 165篇 |
2007年 | 146篇 |
2006年 | 134篇 |
2005年 | 96篇 |
2004年 | 74篇 |
2003年 | 75篇 |
2002年 | 59篇 |
2001年 | 43篇 |
2000年 | 36篇 |
1999年 | 38篇 |
1998年 | 70篇 |
1997年 | 59篇 |
1996年 | 42篇 |
1995年 | 54篇 |
1994年 | 25篇 |
1993年 | 34篇 |
1992年 | 30篇 |
1991年 | 25篇 |
1990年 | 24篇 |
1989年 | 22篇 |
1988年 | 15篇 |
1987年 | 30篇 |
1986年 | 30篇 |
1985年 | 22篇 |
1984年 | 30篇 |
1983年 | 26篇 |
1982年 | 16篇 |
1981年 | 8篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 11篇 |
1976年 | 14篇 |
1975年 | 8篇 |
排序方式: 共有6485条查询结果,搜索用时 15 毫秒
81.
In this study, high density polyethylene (HDPE) was combined with dicumyl peroxide (DCP) to produce crosslinked parts via rotational molding. The effect of DCP content (0.1–2.5 phr) on the crosslinking degree was investigated to determine its effect on the chemical, mechanical, physical, and thermal properties of HDPE. The gel content and crosslink density was found to increase with DCP content. These trends led to a reduction in the degree of crystallinity, melting, and crystallization temperature. Thermogravimetric analysis (TGA) showed that crosslinked HDPE (xHDPE) has higher thermal stability than the neat matrix in both air and nitrogen atmosphere. In addition, a direct relationship was observed between improved thermal resistance and higher impact strength. Finally, relationships between the tensile properties of xHDPE and the degree of crystallinity were observed, which were all controlled by the level of crosslinking. These results have the potential to advance the manufacturing of high performance materials suitable for a wide range of applications such as automotive parts, agricultural products, chemical storage tanks, large waste containers, and fuel tanks in general. 相似文献
82.
J. Mustafa A. Gupta M. S. Ahmad F. Ahmad S. M. Osman 《Journal of the American Oil Chemists' Society》1986,63(9):1191-1192
Seed oils ofGnetum scandens (Gnetaceae) andSterculia pattens (Sterculiaceae) were found to contain sterculic (28.57,6.97) and malvalic (11.27,3.87) acids, respectively. Gas Chromatographic
analysis of silver nitrate/meth-anol-treated methyl esters was used to establish the co-occurrence of these two acids.Sterculia foetida methyl esters were used as a reference standard. 相似文献
83.
S. Afaque M. H. Ansari M. S. Ahmad M. S. Siddiqui 《Journal of the American Oil Chemists' Society》1989,66(9):1334-1337
Substituted oxathiolane and thioether derivatives have been synthesized from an allylic oxo fatty acid ester. The reaction
of methyl 4-oxo-trans-2-octadecenoate with 3-mercaptopropan-1,2-diol (1-thioglycerol) affords methyl 4-(3′-hydroxymethyl-1′,4′-oxathiolane)-2(3)-(O-mercaptopropan-1″,2″-diol)-octadecanoate
(II), methyl 4-oxo-2(3)-(O-mercaptopropan-1′,2′-diol)-octadecanoate (III), methyl 4-(3′-hydroxy-l′,5′-oxathiane)-2 (3)-(S-mercaptopropan-1″,2″-diol)-octadecanoate
(IV), methyl 4-oxo-2(3)-(S-mercaptopropan-1′, 2′diol)-octadecanoate (V) and methyl 4-(3′-hydroxymethyl-1′, 4′-oxathiolane)-2(3)-(S-mercaptopropan-1″,
2″-diol)-octadecanoate (VI). Structures of the individual reaction products have been established on the basis of spectral
data and microanalyses. 相似文献
84.
M. U. Ahmad S. K. Husain S. M. Osman 《Journal of the American Oil Chemists' Society》1981,58(6):673-674
Seed oil ofPhyllanthus niruri (Euphorbiaceae) contains 1.2% ricinoleic (12-hydroxy-cis-9-octadecenoic) acid, previously unknown in the genusPhyllanthus. Identification is based on thin layer and gas liquid chromatography, infrared, nuclear magnetic resonance, and mass spectrometry
analysis as well as chemical methods. Other major components of the oil are linoleic acid (21%) and linolenic acid (51.4%).
Presented at the ISF/AOCS World Congress, April 1980, New York City. 相似文献
85.
Ahmad A. Adewunmi Suzylawati Ismail Abdullah S. Sultan 《Journal of Inorganic and Organometallic Polymers and Materials》2016,26(4):717-737
Interest in the development of polymeric hydrogels impregnated with carbon-nanotubes (CNTs) is growing rapidly in recent times owing to their usefulness in many fields of human endeavor. This review paper serves as an archive of literature reports of several researchers who have worked on polymeric hydrogels embedded with CNTs for diverse applications. The review covers up to date research advancement on the synthesis and characterization properties of CNTs nanocomposite hydrogels. Besides, this review discusses extensively the various fields in which polymeric hydrogels infused with CNTs have been applied. This unprecedented compilation of CNTs nanocomposite hydrogels information into a single revision allows a straightforward comparison of studies performed for diverse applications. 相似文献
86.
Structural Control of NiO–YSZ/LSCF–YSZ Dual‐Layer Hollow Fiber Membrane for Potential Syngas Production
下载免费PDF全文

Mohd Hilmi Mohamed Mohd Hafiz Dzarfan Othman Muhazri Abd Mutalib Mukhlis Rahman Juhana Jaafar Ahmad Fauzi Ismail Mohd Irfan Hatim Mohamed Dzahir 《International Journal of Applied Ceramic Technology》2016,13(5):799-809
The objective of this study was to fabricate dual‐layer hollow fiber as a microreactor for potential syngas production via phase inversion‐based co‐extrusion/cosintering process. As the main challenge of phase inversion is the difficulty to obtain defect‐free fiber, this work focuses on the effect of the fabrication parameters, that is, nonsolvent content, sintering temperature and outer‐layer extrusion rate, on the macrostructure of the produced hollow fiber. SEM images confirm that the addition of nonsolvent has successfully minimized the finger‐like formation. At high sintering temperature, more dense hollow fiber was formed while outer‐layer extrusion rate affects the outer layer thickness. 相似文献
87.
Synthesis and Characterization of NiO Nano‐Spheres by Templating on Chitosan as a Green Precursor
下载免费PDF全文

Cheng Keong Choo Tze Lim Goh Ladan Shahcheraghi Gek Cheng Ngoh Ahmad Zuhairi Abdullah Bahman Amini Horri Babak Salamatinia 《Journal of the American Ceramic Society》2016,99(12):3874-3882
In this study, nickel oxide was prepared through the calcination of extrusion dripped chitosan/nickel nitrate beads. The morphology and structural properties of the products were studied using various characterization techniques. Uniformly distributed nickel oxide was formed as observed from the studies of surface morphology where the processing parameters play a huge role on the resulting morphology. TEM results have shown that nickel oxide with crystallite sizes of 10–30 nm was obtained. The Fourier‐transform infrared spectra studies show an intense peak at 525 cm?1, which is attributed to the vibration of Ni–O bond. Furthermore, the XRD results show NiO diffraction peaks correspond to (111), (200), (220), (311), and (222) which indicates that a bunsenite structure with a face‐centered cubic phase was produced in this study. The usage of 500°C as the lower limit in this study is justified due to the complete removal of the templating material as seen in the thermalgravimetric analysis studies. Furthermore, it was obtained that the largest surface area of nickel oxide synthesized using this technique is 48.024 m2/g with pore sizes of 19.843 nm. The usage of chitosan as a green template for the synthesis of nanoparticles has shown promising results which allows a more economical and sustainable approach for the fabrication of nanomaterials. 相似文献
88.
89.
Sulfonated Beet Pulp as Solid Catalyst in One-Step Esterification of Industrial Palm Fatty Acid Distillate
下载免费PDF全文

Farahnaz Eghbali Babadi Soraya Hosseini Salman Masoudi Soltani Mohamed Kheireddine Aroua Ahmad Shamiri Mahtab Samadi 《Journal of the American Oil Chemists' Society》2016,93(3):319-327
In this research a new heterogeneous catalyst has been prepared for biodiesel production. The catalyst was prepared by sulfonating industrial sugar waste. Unlike homogeneous catalysts, which require further purification and separation from the biodiesel production reaction media, this inexpensive synthetic catalyst does not need to go through an additional separation process. This advantage consequently minimizes the total application costs. The catalyst was prepared by partially carbonizing sugar beet pulp at 400 °C. The carbonization product was then sulfonated with concentrated H2SO4 vapor in order to produce a solid catalyst. The prepared catalyst was used in the esterification reaction between palm fatty acid distillate (PFAD) and methanol. The effects of the temperature, methanol/PFAD ratio, reaction time and catalyst dosage on the efficiency of the production were individually investigated. The optimum biodiesel production occurred at 85 °C, a reaction time of 300 min, catalyst dosage of 3 g and methanol/PFAD ratio of 5:1 (mol/mol), lowering the acid value from 198 to 13.1 (mg KOH/g oil) or the equivalent, with a fatty acid methyl ester yield of around 92 %. The results suggest that the synthesized inexpensive catalyst is useful for biodiesel production from PFAD. 相似文献
90.
Ahmad Jonidi Jafari Babak Kakavandi Roshanak Rezaei Kalantary Hamed Gharibi Anvar Asadi Ali Azari Ali Akbar Babaei Afshin Takdastan 《Korean Journal of Chemical Engineering》2016,33(10):2878-2890
Discharging the effluents of textile wastewaters into potable water resources can endanger the ecosystem, due to their reactivity, toxicity, and chemical stability. In this research, the application of powder activated carbon modified with magnetite nanoparticles (PAC-MNPs) as an adsorbent for removal of reactive dyes (Reactive black 5 (RB5) and reactive red 120 (RR120)) was studied in a batch system. The adsorption performance was evaluated as a function of temperature, contact time and different adsorbent and adsorbate concentrations. The levels of factors were statistically optimized using Box-Behnken Design (BBD) from the response surface methodology (RSM) to maximize the efficiency of the system. The adsorption process of both dyes was fit with the pseudo-second order kinetic and Langmuir isotherm models. The identified optimum conditions of adsorption were 38.7 °C, 46.3 min, 0.8 g/L and 102 mg/L for temperature, contact time, adsorbent dose, and initial dyes concentration, respectively. According to the Langmuir isotherm, the maximum sorption capacities of 175.4 and 172.4 mg/g were obtained for RB5 and RR120, respectively. Thermodynamics studies indicated that the adsorption process of the reactive dyes was spontaneous, feasible, and endothermic. After five cycles, the adsorption efficiency was around 84 and 83% for RB5 and RR120, respectively. A high value of desorption was achieved, suggesting that the PAC-MNPs have a good potential in regeneration and reusability, and also can be effectively utilized in industrial applications. PAC-MNPs also show a good anti-interference potential for removal of reactive dyes in dye-industry wastewaters. 相似文献